This is custom error handler in PHP. You can use your custom error handler for showing the error in you customized format, logging the error in a log file and for other reason.

<?php
//error handler function
function customError($errno, $errstr, $fileName, $lineNo)
{

switch ($errno) {

// fatal error. die it.
case E_USER_ERROR:
echo [...]

In actions.class.php page of symfony framework, you can catch errors and display those errors in template. Set errors in your action/method using:

<?php
if ($error) {
$this->getRequest()->setError(‘userName’, ‘The user Name field cannot be left blank’);
$this->getRequest()->setError(‘email’, ‘The Email field cannot be left blank’);
return false;
}
?>

Return false is important for returning to the same form, from where you get data for [...]

Please, do not forget to read the small updates below on JavaScript debugging. Ya, that is important. Thanks!
First of all I will suggest moving to Firefox browser. There you will get JavaScript console
(Firefox: Tools->JavaScript Console) which is very useful for JavaScript debugging.
Old IE style error message box will not give the correct line number [...]